I am trying to simulate material dumping process from shovel onto mining dump truck. And for that i am using Abaqus/Explicit. When i plot the contact force of material falling onto truck body under gravity, it gives me the maximum value of 0.12e+11, where as a simple theoretical analysis shows that the resulting impact force for 100 tons of material falling under gravity should be 9e5 N. I am not been able to understand the reason that why Abaqus /Explicit is exaggerating the impact/contact force so much. And i dont know how to correct this thing.

I have a bar with an analytical rigid surface attached at the free end with a RP at the centre of it. I am applying a rotational BC of UR3 = 0.017 (1 deg) with respect to the Z axis, but the resulting rotation at the end of the bar is more than 1 degree. Any idea why? Or how to have a full control of the twist of the bar? Also the bar deforms in shape where the end at which the twist is applied expands, making this cross-section bigger (clearly no the deformation expect for torsion). Input file attached in a word doc.